Add per-period concentration-history audit so retroactive reviews can recompute exposure

[thlpkee20-wq]

Description

Concentration limits change over time; today only the latest value is queryable. Persist (period_id -> ConcentrationConfig) history so auditors can recompute concentration violations as of any past period without replaying the chain.

Requirements and context

• Must be secure, tested, and documented
• Should be efficient and easy to review
• Relevant code: Revora-Contracts/src/lib.rs
• History storage must respect contract size budget; cap to last N periods configurable

Suggested execution

• Fork the repo and create a branch
• git checkout -b feat/concentration-history-audit
• Implement changes
  • Add ConcentrationHistory map keyed by period_id
  • Write on every set_concentration_limit and on period close
  • Add view get_concentration_at(offering_id, period_id)
• Validate security and correctness assumptions

Test and commit

• Run tests
  • cargo test --all
• Cover edge cases
  • Lookup beyond retention horizon must return None not a stale default
• Include test output and security notes

Example commit message

feat: persist per-period concentration config for audit lookup

Guidelines

• Minimum 95 percent test coverage
• Clear documentation
• Timeframe: 96 hours

[Abdulmajeed82]

@Abdulmajeed82 has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

I would like to work on this issue pls

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Abdulmajeed82 to this issue.

[drips-wave]

Congratulations, @Abdulmajeed82! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 30, 2026.

🧑‍💻 @Abdulmajeed82: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

Warning

When opening a PR, please link it to this issue to ensure it gets tracked accurately. Points are awarded when this issue is marked as completed by the maintainer.

🤠 Repo maintainers: Please keep an eye on the contributor's progress and review their work before the due date. You can manage this issue, including adjusting its complexity and points, here.

🌊 Happy Wave 🌊